Medical devices that are deployed at a site inside the body must be delivered to the site. For example, stents are cylindrical devices used to maintain the patency of a body passageway, such as a blood vessel or a urethra. A stent is delivered to the location where it is to be deployed on the distal end of a delivery device such as a catheter. During delivery, the stent is maintained in a small caliber conformation. After delivery to the site of deployment, the stent is made or allowed to expand so as to assume a large caliber conformation in the body passageway. Some stents are “self-expanding”, in which case the stent in the large caliber conformation is mechanically restrained in the small caliber conformation in which it is delivered to the site of deployment. After delivery, the restraint is removed so as to allow the stent to assume its large caliber conformation at the site of deployment. It is also known to form a stent from a one-way or two-way shape memory alloy, such as Nitinol™. With this type of stent, the stent is brought from one caliber to another by exposing the stent to a change of temperature, as is known in the art of shape memory stents. Balloon expandable stents, made of a non-shape memory material such as stainless steel, are also known.
U.S. Pat. Nos. 6,221,081 and 6,517,569 to Mikus et al disclose an insertion device in which a stent is mounted onto the distal end of an inner sheath. The stent is surrounded by a “peel-away sheath”, which in turn is surrounded by an outer sheath. After the distal end of the device has been delivered to a body site where the stent is to be deployed, the outer sheath is retracted. The stent is then allowed to assume its large caliber conformation. The “peel-away sheath” is then grasped and manually split by the user as the “peel-away sheath” is removed.
U.S. Pat. No. 6,159,198 to Gardeski et al. discloses an introducing system for introducing electric leads to a body site. The introducer has a hollow sheath through which the leads are delivered to a body site. After the leads have been delivered, the sheath is manually retracted from the body. As the sheath is pulled out of the body it encounters a blade that cuts the sheath longitudinally from its proximal end to its distal end.